MgO–C Refractories with Al2O3 and TiO2 Nano-Additives: Insights from X-Ray Micro-Computed Tomography and Conventional Techniques for Assessing Corrosion and Oxidation

Nondestructive investigation on close and open porosity of additively manufactured parts using an X-ray computed tomography

In-depth quality assessment of 3D-printed parts is vital in determining their overall characteristics. This study focuses on the use of 2D X-Ray diffraction (2D-XRD) and X-Ray micro-computed tomography (micro-CT) techniques to evaluate the crystallography and internal defects of 316L SS parts fabricated by the powder-based direct energy deposition (DED) technique. The test samples were printed in a controlled argon environment with variable laser power and print speeds, using a customized deposition pattern to achieve a high-density print (>99%). Multiple features, including hardness, elastic modulus, porosity, crystallographic orientation, and grain morphology and size were evaluated as a function of print parameters. Micro-CT was used for in-depth internal defect analysis, revealing lack-of-fusion and gas-induced (keyhole) pores and no observable micro-cracks or inclusions in most of the printed body. Some porosity was found mostly concentrated in the initial layers of print and decreased along the build direction. 2D-XRD was used for phase analysis and grain size determination. The phase analysis revealed single phase γ-austenitic FCC phase without any detectable presence of the δ-ferrite phase. A close correlation was found between Electron Backscatter Diffraction (EBSD) and 2D-XRD results on the average size distribution and the crystallographic orientation of grains in the sample. This work demonstrates the fast and reliable as-printed crystallography analysis using 2D-XRD compared to the EBSD technique, with potential for in-line integration.

Effect of the addition of carbon nanotubes on the properties of low carbon Al2O3 refractory materials

The present study aims at evaluating the impact of anobiid damage on pine timber elements. Anobiid attack produces a diffuse damage of the elements with a set of tunnels in random directions and sizes, thus confusing quantification. Therefore, a method was developed based on X-ray micro-computed tomography (μ-XCT) to obtain, for naturally infested timber samples, an empirical correlation between lost material percentage (consumed by beetles) and timber apparent density (original, before degradation—OTD and residual, after degradation—RTD). The quantified density loss can then be used in further assessment of the structure. The results of the tests performed showed high correlation between original apparent density and lost material percentage (r2 = 0.60) and between residual apparent density and lost material percentage (r2 = 0.83), which confirms μ-XCT as a valuable tool to the required quantification. The loss of density results can be further applied on the definition of an assessment method for the evaluation of the residual strength of anobiids infested timber, thus contributing to reducing unnecessary replacement. The optimized procedure of the μ-XCT study for infested Maritime pine (Pinus pinaster) is presented and discussed in this article.

The characterization of some clay as refractory materials for furnace lining has become relevant to find solutions to the cost involved in the purchase and importation of these refractory materials. This work investigated the refractory properties of clay samples for their suitability for use in the industries. Clay samples were collected from Gakem and Abouchiche areas and analysed for physical and chemical properties to determine the suitability of the clays as refractory materials. The results showed cold crushing strength (21.46MN/m2), thermal shock resistance (27 cycles), bulk density (3.52g/cm3), linear shrinkage(3.80%), apparent porosity (28.84%) and permeability (80%) for Gakem; and cold cold crushing strength (18.40MN/m2), thermal shock resistance (25 cycles), bulk density(2.81g/cm3), linear shrinkage (3.70%), apparent porosity (25.86%) and permeability (77%) for Abouchiche respectively. The chemical compositions of these clay samples were also investigated. The results showed that the samples fall under Aluminosilicate type of clay because of their high values of Aluminium Oxide and Silicon Oxide. Tests showed that clay from these areas can be used to produce refractory materials that can withstand a furnace temperature of about 1600°C. http://dx.doi.org/10.4314/njt.v36i3.26

The characterization of some clay as refractory materials for furnace lining has become relevant to find solutions to the cost involved in the purchase and importation of these refractory materials. This work investigated the refractory properties of clay samples for their suitability for use in the industries. Clay samples were collected from Gakem and Abouchiche areas and analysed for physical and chemical properties to determine the suitability of the clays as refractory materials. The results showed cold crushing strength (21.46MN/m 2 ), thermal shock resistance (27 cycles), bulk density (3.52g/cm 3 ), linear shrinkage(3.80%), apparent porosity (28.84%) and permeability (80%) for Gakem; and cold cold crushing strength (18.40MN/m 2 ), thermal shock resistance (25 cycles), bulk density(2.81g/cm 3 ), linear shrinkage (3.70%), apparent porosity (25.86%) and permeability (77%) for Abouchiche respectively. The chemical compositions of these clay samples were also investigated. The results showed that the samples fall under Aluminosilicate type of clay because of their high values of Aluminium Oxide and Silicon Oxide. Tests showed that clay from these areas can be used to produce refractory materials that can withstand a furnace temperature of about 1600°C.  http://dx.doi.org/10.4314/njt.v36i3.26

The anthropogenic CO2 accumulating in the ocean is lowering seawater carbonate ion concentration and may reduce calcification rates of marine calcareous organisms. Several proxies based on test weights of planktic foraminifera have been used to evaluate the impact of ocean acidification on these organisms. Unfortunately, because of the absence of a method to evaluate the bulk density of a test, the impact of seawater carbonate chemistry on test calcification is still not fully understood. In this study, we measured bulk densities of living Globigerina bulloides (planktic foraminifera) tests with an X-ray micro-computed tomography (XMCT) scanner and compared them with ambient seawater characteristics. Results demonstrated that test bulk densities were controlled by ambient seawater carbonate ion concentrations and that changes of test bulk densities were accompanied by changes in micron to submicron scale porosity of internal ultrastructure. These results suggest that alteration of the bulk density of foraminiferal tests due to acidification of ambient seawater can be directly observed by XMCT scanning. A useful metric of calcification intensity would therefore be physical measurements of test densities with XMCT.

The increasing need for refractory bricks has advanced research into the utilization of readily available agricultural by-products. This work examined the influence of cassava peel ash (CPA) and palm kernel ash (PKA) as admixtures on the physical properties of locally produced refractory bricks. Samples coded CTR (Control), clay/30CPA, clay/30PKA, and clay/30CPA-PKA were prepared, moulded by machine, fired at elevated temperature, and tested for bulk density, apparent porosity, and firing shrinkage to assess the influence of addition of agro-wastes. The objective of the study is to determine the effects of addition of CPA, PKA, and its hybrid on mechanical properties of refractory bricks. The result showed that the control sample has the highest density of 2.3 gcm-3 while clay/30CPA, clay/30PKA and clay/30CPA-PKA samples have 2.0, 1.8 and 1.8 gcm-3 respectively. The percent porosities are 19.8, 20.63, 26.51 and 25.5% for CTR, clay/30CPA, clay/30PKA and clay/30CPA-PKA, respectively. Both CTR and clay/30CPA shared similar percent shrinkage of 4.3%, while clay/30PKA and clay/30CPA-PKA had percent shrinkage of 2.17%. The results showed that the addition of the agro-waste additives did not affect the physical integrity of the refractory bricks but showed that clay/30CPA-PKA followed by clay/30PKA are most suitable for the production of insulating refractory bricks, and also fall within the standard values required for fire clay refractory bricks.

The increasing need for refractory bricks has advanced research into the utilization of readily available agricultural by-products. This work examined the influence of cassava peel ash (CPA) and palm kernel ash (PKA) as admixtures on the physical properties of locally produced refractory bricks. Samples coded CTR (Control), clay/30CPA, clay/30PKA, and clay/30CPA-PKA were prepared, moulded by machine, fired at elevated temperature, and tested for bulk density, apparent porosity, and firing shrinkage to assess the influence of addition of agro-wastes. The objective of the study is to determine the effects of addition of CPA, PKA, and its hybrid on mechanical properties of refractory bricks. The result showed that the control sample has the highest density of 2.3 gcm-3 while clay/30CPA, clay/30PKA and clay/30CPA-PKA samples have 2.0, 1.8 and 1.8 gcm-3 respectively. The percent porosities are 19.8, 20.63, 26.51 and 25.5% for CTR, clay/30CPA, clay/30PKA and clay/30CPA-PKA, respectively. Both CTR and clay/30CPA shared similar percent shrinkage of 4.3%, while clay/30PKA and clay/30CPA-PKA had percent shrinkage of 2.17%. The results showed that the addition of the agro-waste additives did not affect the physical integrity of the refractory bricks but showed that clay/30CPA-PKA followed by clay/30PKA are most suitable for the production of insulating refractory bricks, and also fall within the standard values required for fire clay refractory bricks.

Effects of structural defects on low-velocity impact damage mechanisms of three-dimensional braided composites based on X-ray micro-computed tomography

Analyzing the microstructure of a fresh sorbet with X-ray micro-computed tomography: Sampling, acquisition, and image processing

Effects of off-axis angle on shear progressive damage of 3D woven composites with X-ray micro-computed tomography

The influence of the glass-ceramic addition on mechanical properties and microstructural characteristics of porcelain stoneware tiles has been studied. Mechanical characterisation has been carried out on industrial and laboratory porcelain stoneware tiles obtained by mixing glass-ceramic systems to current industrial bodies. Moreover, microstructure and texture have been studied and bulk density, open and close porosity and phase composition determined. Industrial bodies contain very low open porosity (0.2-0.3 vol%) and closed porosity (1.6-4.1%), flexural strength ranging from 30 to 40 MPa, Young modulus from 63 to 71 GPa and Poisson coefficient 0.18. The addition of NAS and KCMAS glass-ceramics precursors led to 3.7-4.3% of residual porosity, flexural strength of 39-43 MPa and Young modulus of 69-73 GPa, equal or higher than the industrial product ones. In standard conditions bodies added with BAS and ZCS glass-ceramics did not come to complete sintering leaving significant residual porosity (12-14%). Flexural strength and Young modulus were rather low (26-29 MPa and 51 GPa, respectively). However, an appropriate mixture of BAS and ZCS systems allowed to achieve excellent mechanical performances (flexural strength 40 MPa, Young modulus 74 GPa, Poisson coefficient 0.26) notwithstanding the remarkable residual porosity (7.3%). (orig.)

The bulk density of grains from a celestial body is a fundamental property related to its composition and structure, contributing to the understanding of its evolutionary history. In this study, we provide the bulk density of 637 grains returned from the C-type near-Earth asteroid 162173 Ryugu. This is the largest number of grains to date for the curation activity, corresponding to 38 wt.% of the total returned samples (approximately 5.4 g). Although several densities of the Ryugu grains were reported, the volume estimation of some samples showed uncertainties. Therefore, we applied a new volume estimation model calibrated by X-ray micro-computed tomography (XCT) to the Ryugu grains to more accurately estimate their bulk density. The obtained average bulk density of 637 Ryugu grains was 1.79 ± 0.31 g/cm3 (1σ variation) for weights of 0.5‒100 mg (sub-mm ‒to 10 mm) irrespective of their 3D shapes characterized by three axial length ratios, considered to be a representative of the returned samples. The bulk density distributions of the grains in Chambers A and C were statistically distinguishable, with mean values of 1.81 ± 0.30 and 1.76 ± 0.33 g/cm3 (1σ variations), respectively. Despite the small difference, bulk density may have differed by sampling site. The obtained average bulk density value of A + C samples was almost the same as that of 16 Ryugu grains estimated based on CT scanned data, and was consistent with the densities of CI chondrites (1.57–1.91 g/cm3). The axial ratios of the grains in Chambers A and C were similar and those of the 724 returned samples and the flying particles ejected during the sampling operations were also similar, suggesting that relatively small Ryugu materials (mm‒cm in size) are similar in shape. The minor difference between the Rygu grains and flying particles could be attributed to events such as scraping during sampling operations and transportation.Graphical

Ti6Al4V is a suitable titanium alloy for all kinds of medical implants and prostheses because of its high durability and biocompatibility. Furthermore, components of high complexity can be produced via additive manufacturing which allows for more flexibility and easy prototyping of patient specific implants. However, this flexibility implies the risk of internal defects resulting from the manufacturing process. The nondestructive investigation of critical components is therefore crucial to avoid premature failure. X-ray micro-computed tomography (XCT) is a method that can resolve internal structures three dimensionally in a non-destructive way. Nevertheless, the probability to detect defects is limited by the achievable resolution and image quality of a scan. In this contribution, we performed a systematic study to determine the pore size distribution in additively manufactured Ti6Al4V parts using XCT. We focused on the influence of scanning parameters such as voxel size, tube voltage and current on the image quality that determines the outcome of the porosity analysis. Image quality was assessed via contrast to noise ratio (CNR) and slanted-edge modulation transfer function (MTF) according to ISO 12233. Furthermore, we optimized the beam hardening correction for the scans and investigated influences of different image denoising algorithms. Results showed that tube voltage and current greatly influence the CNR of the data set while the MTF is, within limits, almost constant as long as the electron beam focus is optimized. With higher physical resolution, smaller defects can be detected, which leads to porosity values of 0.36, 1.35 and 2.54% at 10, 5 and 2.5 μm resolution respectively. Image post-processing can further influence porosity outcome because of the segmentation of noise induced particles. Different image denoising algorithms therefore can heavily reduce porosity values depending on spatial resolution.